Witnesses testify that half of Guantánamo Bay's prisoners are on hunger strike, some with serious health risks. Photograph: Brennan Linsley/AP

Reports are emerging from the US military prison at Guantánamo Bay that a majority of the prisoners are on a hunger strike. Of the detainees, 166 remain locked up, although more than half have been cleared by the Obama administration for release. Yet, there they languish – in some cases, now in their second decade – in a hellish legal limbo, uncharged yet imprisoned.

"We are in danger. One of the soldiers fired on one of the brothers a month ago. Before that, they send the emergency forces with M-16 weapons into one of the brothers' cell blocks … Now they want to return us to the darkest days under Bush. They said this to us. Please do something."

Al-Marwalah was referring to the first recorded use of rubber bullets being fired at a Guantanamo prisoner by the US military guards there.

According to Pardiss Kebriaei, a senior staff attorney with the Center for Constitutional Rights, her client Ghaleb al-Bihani is one of the Guantánamo prisoners currently on a hunger strike. She told me what al-Bihani related to her:

"There is a large-scale hunger strike in Camp 6, which is the largest of the facilities at Guantánamo. That prison holds about 130 men. He said that almost everyone, except for a few who are sick and elderly, is on strike. He had lost over 20 pounds. He is a diabetic. His blood-glucose levels are fluctuating wildly. He told me that medical staff at Guantánamo has told him his life is in danger. And he and others want us to get the word out about this."

Meanwhile, in Washington, DC this week, the Obama administration has to defend its Guantánamo policy before a hearing of the Inter-American Commission on Human Rights, a part of the Organization of American States. Kebriaei's colleague at the Center for Constitutional Rights, attorney Omar Farah, addressed the hearing, saying:

"I represent Tariq Ba Odah, a young Yemeni man who's been on an uninterrupted hunger strike since February 2007. He is force-fed daily by Guantánamo guard staff. As we speak, it's likely that he's being removed from his cell, strapped to a restraint chair, and a rubber tube is being inserted into his nose to pump a liquid dietary supplement into his stomach.

"Tariq says this is the only way that he has to communicate to those of us who have our freedom what it means to be unjustly detained, to be put in a cell for a decade without charge. It's his only way to communicate the barbarism of such conduct."

The Obama administration has claimed that only six or seven prisoners are on a hunger strike. Prisoner letters and attorney eyewitness accounts, however, support the claim that well over 100 of the 166 Guantánamo prisoners are into at least the second month of the strike.

Another lawyer for Guantánamo prisoners, Kristine Huskey of Physicians for Human Rights, also testified Tuesday. She later explained that indefinite detention causes:

"Severe and lasting psychological trauma … caused by chronic states of stress, anxiety and dread, because these people at Guantánamo don't know if they're going to be released, if ever … all of this uncertainty and uncontrollability causes extreme stress on the immune system, the cardiovascular system. It leads to asthma, diabetes, gastrointestinal disorders, spread of cancer, viral infections, hypertension, depression, suicide, PTSD."

"The United States only detains individuals when that detention is lawful, and does not intend to hold any individual longer than necessary."

In his testimony, CCR attorney Omar Farah countered:

"In light of the existential torment that indefinite detention creates for Guantánamo prisoners and the physical risks that it poses; in light of the fact that the state itself has conceded that more than half of the prisoners the state no longer has an interest in detaining, through the clearances that my colleague just described; in light of the fact that nine prisoners have died at Guantánamo in US custody – and after 11 years, when is enough enough?"

The Guantánamo prisoners' hunger strike is a bold, desperate, life-threatening act of defiance, which Obama should immediately address by fulfilling one of his first executive orders as president: to close Guantánamo.